ABCR expression in foveal cone photoreceptors and its role in Stargardt macular dystrophy

Mutations in the gene encoding ABCR are responsible for Stargardt macular dystrophy. Here we show by immunofluorescence microscopy and western-blot analysis that ABCR is present in foveal and peripheral cone, as well as rod, photoreceptors. Our results suggest that the loss in central vision experienced by Stargardt patients arises directly from ABCR-mediated foveal cone degeneration.     

好氧颗粒污泥的研究

好氧颗粒污泥是一种全新概念的污水生物处理技术。介绍了好氧颗粒污泥技术的理论基础,包括好氧污泥形成机理及理化特性研究,探讨了影响好氧颗粒污泥形成的因素以及工业应用的方向和前景。     

Historical and other considerations regarding the crystal form of sodium-ammonium d- and l-tartrate,potassium d- and l-tartrate,potassium-ammonium d- and l-tartrate,and potassium racemate.—II

In 1914, the physics discipline had reached a very similar stage of development in Australia and Japan. A generation later the paths of development had considerably diverged. A systematic comparison of the evolution of physics in the two countries during these years identifies factors—political, economic and cultural—that led to this divergence, but it also uncovers a number of underlying parallels.     

The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry

Cyclic nucleotide-gated (CNG) channels are crucial for visual and olfactory transductions. These channels are tetramers and in their native forms are composed of A and B subunits, with a stoichiometry thought to be 2A:2B (refs 6, 7). Here we report the identification of a leucine-zipper-homology domain named CLZ (for carboxy-terminal leucine zipper). This domain is present in the distal C terminus of CNG channel A subunits but is absent from B subunits, and mediates an inter-subunit interaction. With cross-linking, non-denaturing gel electrophoresis and analytical centrifugation, this CLZ domain was found to mediate a trimeric interaction. In addition, a mutant cone CNG channel A subunit with its CLZ domain replaced by a generic trimeric leucine zipper produced channels that behaved much like the wild type, but less so if replaced by a dimeric or tetrameric leucine zipper. This A-subunit-only, trimeric interaction suggests that heteromeric CNG channels actually adopt a 3A:1B stoichiometry. Biochemical analysis of the purified bovine rod CNG channel confirmed this conclusion. This revised stoichiometry provides a new foundation for understanding the structure and function of the CNG channel family.     

Rom-1 is required for rod photoreceptor viability and the regulation of disk morphogenesis

The homologous membrane proteins Rom-1 and peripherin-2 are localized to the disk rims of photoreceptor outer segments (OSs), where they associate as tetramers and larger oligomers. Disk rims are thought to be critical for disk morphogenesis, OS renewal and the maintenance of OS structure, but the molecules which regulate these processes are unknown. Although peripherin-2 is known to be required for OS formation (because Prph2-/- mice do not form OSs; ref. 6), and mutations in RDS (the human homologue of Prph2) cause retinal degeneration, the relationship of Rom-1 to these processes is uncertain. Here we show that Rom1-/- mice form OSs in which peripherin-2 homotetramers are localized to the disk rims, indicating that peripherin-2 alone is sufficient for both disk and OS morphogenesis. The disks produced in Rom1-/- mice were large, rod OSs were highly disorganized (a phenotype which largely normalized with age) and rod photoreceptors died slowly by apoptosis. Furthermore, the maximal photoresponse of Rom1-/- rod photoreceptors was lower than that of controls. We conclude that Rom-1 is required for the regulation of disk morphogenesis and the viability of mammalian rod photoreceptors, and that mutations in human ROM1 may cause recessive photoreceptor degeneration.